If someone pays me in BTC, how do I give them a receipt? Does it prove that a transaction between us took place?
imo, giving someone a unique payment address and its txid hash is good enough as proof of transaction
if you want to go further, you can
sign a message from that receiving address saying,
"I acknowledge the payment of <amount> BTC with transaction id <txid-hash> to my bitcoin address <btc-address>" For example, can the person provide this as proof that they paid me? I suppose the address needs to be tied to my identity. I don't know how that works. Any insight appreciated.
the transaction id in the blockchain is enough to proof they made a payment
but do you really want to
expose your real identity on a
pseudonymous payment system?